External Button Processor with a Rechargeable Battery

ABSTRACT

An external processor device is described for an implantable prosthetic system. An external processor housing has a generally planar skin contacting surface and a central axis perpendicular to the skin contacting surface. A signal processor is located within the processor housing for developing an implant data signal. The processor housing also contains a transmitter coil for coupling the implant data signal across the skin to the implantable prosthetic system. A battery compartment is also located within the processor housing in an annular region around the central axis for containing a battery arrangement to provide electrical power to the signal processor and the transmitter coil.

This application claims priority from U.S. Provisional PatentApplication 61/087,276, filed Aug. 8, 2008, which is incorporated hereinby reference.

FIELD OF THE INVENTION

The invention generally relates to implantable prosthetic systems suchas cochlear implants, and specifically to the external structures ofsuch systems.

BACKGROUND ART

A normal ear transmits sounds as shown in FIG. 1 through the outer ear101 to the tympanic membrane (eardrum) 102, which moves the bones of themiddle ear 103 (malleus, incus, and stapes) that vibrate the oval windowand round window openings of the cochlea 104. The cochlea 104 is a longnarrow duct wound spirally about its axis for approximately two and ahalf turns. It includes an upper channel known as the scala vestibuliand a lower channel known as the scala tympani, which are connected bythe cochlear duct. The cochlea 104 forms an upright spiraling cone witha center called the modiolar where the spiral ganglion cells of theacoustic nerve 113 reside. In response to received sounds transmitted bythe middle ear 103, the fluid-filled cochlea 104 functions as atransducer to generate electric pulses which are transmitted to thecochlear nerve 113, and ultimately to the brain.

Hearing is impaired when there are problems in the ability to transduceexternal sounds into meaningful action potentials along the neuralsubstrate of the cochlea 104. To improve impaired hearing, auditoryprostheses have been developed. For example, when the impairment isrelated to operation of the middle ear 103, a conventional hearing aidmay be used to provide acoustic-mechanical stimulation to the auditorysystem in the form of amplified sound. Or when the impairment isassociated with the cochlea 104, a cochlear implant with an implantedstimulation electrode can electrically stimulate auditory nerve tissuewith small currents delivered by multiple electrode contacts distributedalong the electrode.

FIG. 1 also shows some components of a typical cochlear implant systemwhich includes an external microphone that provides an audio signalinput to an external signal processor 111 where various signalprocessing schemes can be implemented. The processed signal is thenconverted into a digital data format, such as a sequence of data frames,for transmission into the implant 108. Besides receiving the processedaudio information, the implant 108 also performs additional signalprocessing such as error correction, pulse formation, etc., and producesa stimulation pattern (based on the extracted audio information) that issent through an electrode lead 109 to an implanted electrode array 110.Typically, this electrode array 110 includes multiple electrodes on itssurface that provide selective stimulation of the cochlea 104.

Existing cochlear implant systems need to deliver electrical power fromoutside the body through the skin to satisfy the power requirements ofthe implanted portion of the system. FIG. 1 shows a typical arrangementbased on inductive coupling through the skin to transfer both therequired electrical power and the processed audio information. As shownin FIG. 1, an external transmitter coil 107 (coupled to the externalsignal processor) is placed on the skin adjacent to a subcutaneousreceiver coil in the implant 108. Often, a magnet in the external coilstructure interacts with a corresponding magnet in the subcutaneoussecondary coil structure. This arrangement inductively couples a radiofrequency (rf) electrical signal to the receiver in the implant 108,which is able to extract from the rf signal both the audio informationfor the implanted portion of the system and a power component to powerthe implanted system.

In most prior systems, the external components generally have been heldin separate housings so that the external transmitter coil 107 would notbe in the same physical housing as the power source or the externalsignal processor. The various different physical components wouldgenerally be connected by hard wire, although some systems used wirelesslinks between separate external components. A few systems have beenproposed in which all of the external components such as an externalprocessor and a rechargeable battery could be placed within a singlehousing. See U.S. Patent Publication 20080002834 (Hochmair) and U.S.Patent Publication 20070053534 (Kiratzidis), which are incorporatedherein by reference.

The rechargeable batteries (e.g. Lithium-Ion batteries) for such systemshave conductive band materials such as aluminum and copper which arecoated with battery chemistry (e.g. graphite) and are stacked on top ofeach other. But when such a battery is placed within a magnetic fieldgenerated by a current-carrying coil, the conductive band materialsgenerate undesired eddy currents. Excessive eddy currents are asignificant problem because they cause decreased coupling which reducesefficiency.

U.S. Pat. No. 6,067,474 by Schulman et al. teaches a coil design in theform of a long ribbon of battery electrodes. Conductive band materialsare wound in a spiral (see FIGS. 7 and 9) so that the magnetic fieldlines generated by a coil are parallel to the conductive band materialsthereby reducing eddy currents. One drawback of this approach is that inthe region of overlapping conductive band materials, adjacent cathodic(46′) and anodic (48′) bands (separated by an insulator material (50′,52′)) act as parallel plate capacitors. Such capacitance in turn mayseriously increase the impedance of the coil and thereby reduce theefficiency of data and power transmission between the external coil andthe implanted coil.

SUMMARY OF THE INVENTION

Embodiments of the invention are directed to an external processordevice for an implantable prosthetic system. An external processorhousing has a generally planar skin contacting surface and a centralaxis perpendicular to the skin contacting surface. A signal processor islocated within the processor housing for developing an implant datasignal. The processor housing also contains a transmitter coil forcoupling the implant data signal across the skin to the implantableprosthetic system. A battery compartment is located within the processorhousing in an annular region around the central axis and contains abattery arrangement to provide electrical power to the signal processorand the transmitter coil. An external positioning magnet is radiallyinward of the battery compartment for magnetically interacting with acorresponding internal positioning magnet in the implantable prostheticsystem to hold the device in a fixed position on the skin.

The battery arrangement may be rechargeable. The battery arrangement mayinclude at least one battery cell having multiple conductive band platesarranged to be parallel to magnetic field lines which originate from thetransmitter coil. The battery arrangement may also include multiplebattery cells, each of which occupies a partial annular section withinthe battery compartment. In such an embodiment, each battery cell mayhave the same size, or one of the battery cells may be larger than theothers. The battery compartment may form a complete annular ring aroundthe central axis, or a partial annular section about the central axis.The device may further have a center of mass displaced from the centralaxis so as to define a preferred rotational position of the device onthe skin with the center of mass below the central axis.

The implantable prosthetic system may be a cochlear implant system.Embodiments of the invention also include a replacement batteryarrangement for a device according to any of the above. Embodiments alsoinclude an implantable device having such a battery arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a human auditory system with a cochlear implant.

FIG. 2 shows various elements in a system having an external deviceaccording to one embodiment of the present invention.

FIG. 3 shows front and side views of the transmitter coil and theresulting lines of magnetic force.

FIG. 4 shows a side view as in FIG. 3 with the addition of a processorhousing according to one embodiment.

FIG. 5 shows detail regarding the arrangement of conductive bandmaterials in a battery cell according to one embodiment.

FIG. 6 shows the arrangement of multiple battery plates in a batterycell.

FIG. 7 shows the reduced height of the processor housing due to theimproved arrangement of the battery.

FIG. 8 shows the arrangement of multiple battery cells in annularsections around the central axis.

FIG. 9 shows how embodiments of the present invention displace thecenter of mass away from the central axis to define a preferredrotational position.

FIG. 10 shows an example of an implantable device having a batteryarrangement according to an embodiment of the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Embodiments of the present invention are directed to a novel batteryarrangement for an external processor housing of an implant system thatreduces the influence of eddy currents in inductively coupled coils. Thecapacitive effects of the battery arrangement are minimized and arotational position is defined for the processor housing.

FIG. 2 shows elements of an embodiment in which an external processorhousing 200 has a generally planar skin contacting surface 212 and acentral axis 213 that is perpendicular to the skin contacting surface. Asignal processor 209 is located within the processor housing 200 fordeveloping an implant data signal. The processor housing 200 alsocontains a transmitter coil 208 for coupling the implant data signalacross the skin 207. A rechargeable battery arrangement 214 is containedwithin a battery compartment 210 which is located in an annular regionaround the central axis 213. The battery compartment 210 may form acomplete annular ring around the central axis 213, or a partial annularsection about the central axis 213.

The battery arrangement 214 provides electrical power to the signalprocessor 209 and the transmitter coil 208. An external positioningmagnet 211 is located radially inward of the battery compartment 210 andmagnetically interacts with a corresponding internal positioning magnet202 to hold the external transmitter coil 208 in a fixed position on theskin 207 over an implant coil 203 having its own implant holding magnet202. By this arrangement, the implant data signal is coupled by thetransmitter coil 208 across the skin 207 to the implant coil 203. Theimplant coil 203 is connected by implanted wires 204 to an implantprocessor 206 which develops a stimulation signal for the implantedelectrode array 205 which stimulates audio nerve tissue in the cochlea.

FIG. 3 shows front and side views of the transmitter coil 208 along witha depiction of the lines of the magnetic field produced by the coil whentransmitting the implant data signal. FIG. 4 shows a side view of thesame thing with the addition of the battery compartment 210 and showingthat the battery arrangement 214 includes multiple conductive bandplates 400 arranged to be parallel to the magnetic field lines thatoriginate from the transmitter coil 208. FIGS. 5 provides further detailof the arrangement of the conductive plates showing a cathode band 503and an anode band 502 which are separated by a u-shaped non-conductiveseparator band 501. As shown in FIG. 6, an actual battery cell wouldhave multiple such bands forming multiple anode plates 602 and cathodeplates 603 separated by multiple non-conductive separator plates 601.

FIG. 7 shows how such an annular battery arrangement enables a lowerheight profile for the external processor housing. The height h1 of anexternal processor housing according to an embodiment of the presentinvention as in FIG. 7 A is significantly less than the height h2 of aprior art external processor housing as shown in FIG. 7 B. Although therelative structures of the external holding magnet 702 and transmittercoils 703 is the same in both, in the prior art arrangement as shown inFIG. 7 B, the battery 701 fits over the holding magnet 702, whereas inan embodiment of the present invention as shown in FIG. 7 A, the battery701 does not fit over the holding magnet 702 but instead occupies anannular region radially outward of the magnet.

As shown in FIG. 8, the battery arrangement may include multiple batterycells 801, each of which occupies an annular section within the batterycompartment. Such arrangements reduce capacitive effects in regions ofoverlapping conductive cathodic and anodic band materials, which in turnminimizes undesired eddy currents and leads to greater efficiency. Insuch an embodiment, each battery cell 801 may have the same size, or insome embodiments, one of the battery cells 801 may be larger than theothers thereby defining a preferred rotational position due to theresulting shift in the center of mass away from the central axis. Asshown in FIG. 9, the external processor device may have a center of massdisplaced from the central axis so as to define a preferred rotationalposition of the device on the skin with the center of mass below thecentral axis. Alternatively the holding magnet or some other relativelyheavy component could be offset from the central axis to define apreferred rotational position.

As shown in FIG. 10, the same principles can be used in an implanthaving receiving coils and a rechargeable battery. FIG. 10 shows animplantable housing 1001 for a cochlear implant system having astimulator module 1005 that develops the received implant data signalinto one or more electrical stimulation signals for application to audionerve tissue, e.g., in the cochlear of the patient. An implant holdingmagnet 1003 is surrounded by implant coils 1004 and the rechargeableimplant battery 1002 overlays the implant coils 1004 in an annularregion around the implant holding magnet 1003. As with the externalhousing arrangements discussed above, the implant battery 1002 may bearranged in one or more battery cells in a complete annular ring, or ina partial annular section.

Although various exemplary embodiments of the invention have beendisclosed, it should be apparent to those skilled in the art thatvarious changes and modifications can be made which will achieve some ofthe advantages of the invention without departing from the true scope ofthe invention. For example, embodiments of the invention also include areplacement battery arrangement for a device according to any of theabove.

1. An external processor device for an implantable prosthetic system,the device comprising: an external processor housing having a generallyplanar skin contacting surface and a central axis perpendicular to theskin contacting surface; a signal processor within the processor housingfor developing an implant data signal; a transmitter coil within theprocessor housing for coupling the implant data signal across the skinto the implantable prosthetic system; and a battery compartment withinthe processor housing in an annular region around the central axis forcontaining a battery arrangement to provide electrical power to thesignal processor and the transmitter coil.
 2. A device according toclaim 1, further comprising: an external positioning magnet radiallyinward of the battery compartment for magnetically interacting with acorresponding internal positioning magnet in the implantable prostheticsystem to hold the device in a fixed position on the skin.
 3. A deviceaccording to claim 2, wherein the battery arrangement includes at leastone battery cell having a plurality of conductive band plates arrangedto be parallel to magnetic field lines which originate from thetransmitter coil.
 4. A device according to claim 3, wherein the batteryarrangement includes a plurality of battery cells, each cell occupyingan annular section within the battery compartment.
 5. A device accordingto claim 4, wherein each battery cell has the same size.
 6. A deviceaccording to claim 4, wherein one of the battery cells is larger thanthe others.
 7. A device according to claim 1, wherein the device has acenter of mass displaced from the central axis so as to define apreferred rotational position of the device on the skin with the centerof mass below the central axis.
 8. A device according to claim 1,wherein the battery compartment forms a complete annular ring around thecentral axis.
 9. A device according to claim 1, wherein the batterycompartment forms a partial annular section about the central axis. 10.A device according to claim 1, wherein the battery arrangement isrechargeable.
 11. A device according to claim 1, wherein the implantableprosthetic system is a cochlear implant system.
 12. A replacementbattery arrangement for a device according to any of claims 1-11.